Visible light-mediated transition metal photocatalyst-free acylation/alkylation of para-quinone methides with unstrained ketone

α,α′-Diaryl-substituted carbonyl compounds are important organic intermediates. Current methods for their synthesis mainly focus on aryl aldehydes, carboxylic acids, or aromatic α-keto acids. These three are employed as benzoyl radical precursors and reacted with para-quinone methides (p-QMs) through 1,6-conjugate addition/aromatization to yield α,α′-diaryl-substituted carbonyl compounds. However, the application of this method is limited due to its harsh reaction conditions and the use of precious metals and expensive ligands. Herein, we present a transition metal photocatalyst and additive-free radical cross-coupling of unstrained ketone with p-QMs to explore alternative synthetic methods with mild reaction conditions and new substrate types. A benzoyl group could be introduced at the benzyl position using dihydroquinazolinone derived from unstrained ketone as a benzoyl radical precursor and reacting it with p-QMs under photocatalysis. We utilized cheap and readily available unstrained ketone as acyl radical sources for the 1,6-conjugate addition of p-QMs to obtain α,α′-diarylated carbonyl compounds. The transformation shows a broad substrate scope. Various substituted aryl ketones can be obtained. To our surprise, when utilizing trifluoroacetophenone and 2,2-difluoroacetophenone as raw materials for reaction with p-QMs, fluorine-containing compounds were acquired instead of α,α′-diaryl-substituted carbonyl compounds. Notably, dihydroquinazolinones could participate in the next reaction without complicated posttreatment, and the reaction can be applied on a large scale of 9 mmol.